Ambient lighting in automotive applications is nowadays achieved by providing one or more-colour-light emitting diodes (LEDs) located in various positions in the car. Each of the LEDs is individually controlled in intensity and colour by an integrated circuit (IC) via a communication interface. The LEDs must be calibrated by means of the IC before use to a given target value. A diagnosis of the connected one or more colour LED must be performed during operation.
In today's applications the ambient lighting functionality is assembled on a single Printed Circuit Board (PCB), which requires a certain amount of space. For some applications it requires too big a space, especially if LEDs (and their controlling units) are very close to one another. Hence, there is a constant need to reduce the space occupied by the one or more colour-light emitting diodes significantly by further integration.
It is known that LEDs as a light source produce a significant heat. In classic approaches a heat sink and a good thermal contact are applied to these applications. It is obvious, that a certain space for the heat sink is needed. This might be challenging in case of space limitations. Material like copper or aluminium for the heat sink is needed. Another way to solve the heat problem is the use of LEDs in a bigger matrix. The LEDs are usually put in a big matrix configuration over a given area, so that heat is not generated on a single point for the full power, but distributed over the area. This leads to a lower junction temperature of the LEDs and a longer life time. The use of so called micro-LEDs, i.e. very small LEDs, has been suggested for that purpose. Space saving has also been a motivation to apply semiconductor technology for interconnecting the LEDs, as bonding the micro-LEDs would take too much space.
The controlling of LEDs is for example described in application EP2854483, which discloses an illumination device comprising a plurality of LEDs of various colours and drivers. The device comprises a number of switches/regulators interconnected in a circuit. The switches are part of a driver. An associated controller takes care of aperiodically and independently opening and closing the switch or regulator. The controller generates a variety of PWM signals, each corresponding to a respective colour of the plurality of LEDs of different colours.
In U.S. Pat. No. 7,598,681 B2 is disclosed an integrated circuit to control at least one illumination source. The integrated circuit includes a clock generating circuit coupled to a data reception circuit for extracting information from serial data input to the integrated circuit in coordination with a clock pulse generated by the clock generating circuit. An illumination control signal generation circuit generates at least one illumination control signal to control the at least one illumination source based on the extracted information.
Hence, there is a need for a LED device which meets the limited space requirements and allows controlling the LEDs of the device.